Dirac Research Ab

Lars-Johan Brännmark

Anders Ahlen

Anders Ahlén

Adrian Bahne

Jakob Ågren

Mikael Sternad

Viktor Gunnarsson

Frans Rosencrantz

Mathias Johansson

Denys Volkov

There is provided a method for controlling bass reproduction properties of a multichannel audio system, wherein the audio system has inputs for at least two audio input signals and includes a set of loudspeakers, including at least one bass-capable loudspeaker and at least two high-range loudspeakers, each loudspeaker being associated with a loudspeaker channel. The method includes obtaining impulse responses or transfer functions that represent the sound reproduction properties of each loudspeaker channel at a number of measurement or control positions. The method also includes tuning, when the audio system includes more than one bass-capable loudspeaker, loudspeaker channels of at least two bass loudspeakers to each other so that their sum impulse response has minimum spatial variability, and/or controlling high-range loudspeaker speaker channels to be in-phase with each other and/or with bass-capable loudspeaker channel in a crossover frequency band.

Bass management in audio systems

There is provided a method and corresponding system for determining phase adjustment filters for an associated sound generating system including at least two audio reproduction channels Cand Cwhere each of the audio reproduction channels Cand Chas an input signal and at least one loudspeaker located in a listening environment. The method includes estimating, for each of the audio reproduction channels Cand C, an acoustic transfer function at each of M&#x2265;1 spatial positions in the listening environment, based on sound measurements at the spatial positions; and determining, based on the acoustic transfer functions, phase adjustment filters Fand to be applied, respectively, to the audio reproduction channels Cand C, to reduce the inter-loudspeaker differential phase, IDP, between the audio reproduction channels Cand Cin p listener positions.

Reducing the phase difference between audio channels at multiple spatial positions

Disclosed is a method and a system to determine an audio precompensation controller for an associated sound generating system including a total of N&#x2267;2 loudspeakers, each having a loudspeaker input. The audio precompensation controller has a number L&#x2267;1 inputs for L input signals and N outputs for N controller output signals, one to each loudspeaker. For each one of at least a subset of the N loudspeaker inputs, an impulse response is estimated at each measurement position. For each one of the L input signal(s), a selected one of the N loudspeakers is specified as a primary loudspeaker and a selected subset S including at least one of the N loudspeakers as support loudspeaker(s).

Audio precompensation controller design using a variable set of support loudspeakers

The proposed technology provides an audio decoder () configured to receive input signals representative of at least two audio input channels. The audio decoder is configured to provide direct signal paths and cross-feed signal paths () for the input signals. The audio decoder is configured to apply head shadowing filters () in the direct signal paths and cross-feed signal paths for simulating head shadowing of loudspeakers placed at different angles to an intended listener. The audio decoder is also configured to apply phase shift filters () in the direct signal paths and cross-feed signal paths for introducing a phase difference between the direct signal paths and the cross-feed signal paths representing a phase difference occurring between the ears of the intended listener. The audio decoder is further configured to sum () the direct and cross-feed signal paths to provide output signals.

Audio decoder configured to convert audio input channels for headphone listening

A method for determining an audio precompensation controller for an associated sound generating system comprising a total of N&#x2267;2 loudspeakers, each having a loudspeaker input. The audio precompensation controller has a number L&#x2267;2 inputs for L input signal(s) and N outputs for N controller output signals, one to each loudspeaker. It is relevant to: estimate (S), for each one of at least a subset of the N loudspeaker inputs, an impulse response at each measurement position; specify (S), for each one of the L input signal(s), a selected one of the N loudspeakers as a primary loudspeaker and optionally a selected subset S including at least one of the N loudspeakers as support loudspeaker(s); select (S) at least one loudspeaker pair, that is required to be symmetrical with respect to the listing position; and specify (S), for each primary loudspeaker, a target impulse response at each measurement position.

Audio precompensation controller design with pairwise loudspeaker channel similarity

A scheme to design an audio precompensation controller for a multichannel audio system, with a prescribed number N of loudspeakers in prescribed positions so that listeners positioned in any of P&#x3e;1 spatially extended listening regions should be given the illusion of being in another acoustic environment that has L sound sources located at prescribed positions in a prescribed room acoustics. The method provides a unified joint solution to the problems of equalizer design, crossover design, delay and level calibration, sum-response optimization and up-mixing. A multi-input multi-output audio precompensation controller is designed for an associated sound generating system including a limited number of loudspeaker inputs for emulating a number of virtual sound sources. Method includes: estimating, for each loudspeaker input signals, an impulse response at each of a set of measurement positions that cover the P listening regions; specifying a target impulse response (target stages) for each virtual sound source at each measurement position; and determining adjustable filter parameters of the audio precompensation controller so that a criterion function is optimized.

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Uppsala, Sweden

Lars-Johan Brännmark